A. Field of the Invention
The invention generally concerns small molecules and related oligomers that have selenium or tellurium or both incorporated therein. These compounds have electron rich and electron deficient regions and can be used in organic electronic applications.
B. Description of Related Art
The search for more efficient and economically viable electronic devices is an ongoing process. This is especially the case for organic electronic applications (e.g., both photovoltaic and non-photovoltaic applications).
Organic photovoltaic (OPV) and non-OPV electronic devices based upon bulk heterojunction (BHJ) architectures are considered to be an ideal format to harvest radiation due to their low cost of fabrication, flexibility, and atom economic power conversion efficiency (PCE) compared to their inorganic analogues. The energy gap between the highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) of organic light harvesting materials (polymers, oligomers, and small molecules) dictates their light harvesting capabilities. The electronic structure also influences the charge carrier mobility of both electrons and holes.
The use of small organic molecules in the active layer in the BHJ is being considered as an intriguing alternative to more commonly used high molecular weight organic polymer-based counterparts. Compared to conjugated polymers, small molecules offer a higher degree of control over synthetic methodology, and easier characterization, purification and solution-based processing. Although in many instances energy output from small molecule BHJ-based electronic devices is comparable to polymer-based counterparts, they still fall below the maximum theoretically predicated efficiencies of 10-12%. The development of small molecule BHJ-based devices has been slowed down due to the lack of availability of suitable organic small molecules that have the appropriate optical and electronic properties to deliver the maximum PCE. The current limitations of existing small molecules and oligomers include complex synthetic procedures and purification methods, poor solubility parameters, and minimal control over optical and electronic properties.